Fluorescent tube



Dec. 13, 1955 R. L. LONGINI FLUORESCENT TUBE Filed Dec. 22. 1951WITNESSES:

W D%--%%MM INVENTOR Richard L. Longini BY ATTORN EY United States Patent0 FLUORESCENT TUBE Richard L. Longini, Forest Hiils, Pa, assignor toWestinghouse Electric Corporation, East Pittsburgh, P1, a corporation ofPennsyivania Appiication December 22, 1951, Serial No. 262,937

11 Claims. (Ci. 250-217) My invention relates to electron tubes and inparticular relates to image pickup devices for television and similarpurposes. Such devices comprise, in general, a photoelectric screen onwhich the light field to be transmitted is focused, arrangements whichproduce an electron field which corresponds in space distribution to thelight field, :I?

a scanning means which produces a current which varies in time in thesame way that the electron image varies in space, and some means foramplifying this current. Several different structural arrangementsmeeting these general requirements have been used from time to time, andin some of these, notably the most sensitive such as that called theImage Orthicon, all of the above-mentioned components are embodiedwithin a single evacuated tube. The individual components are delicateand complex in operation, and each one must meet precise standfa tubeunit can be accepted is reduced, and the cost of any tube unit which hasto be rejected as faulty is reduced.

Another object of my invention is to provide a system in which certainof the functions heretofore performed by components of special formbuilt into the composite structure may be carried out by separate tubesof standard types already developed and marketed at low price for otheruses.

Another object of my invention is to provide a novel arrangement forcarry ng out the function of translating the space distribution of aradiation field into time variation of a control current.

Other objects of my invention will become apparent to those skilled inthe art upon reading the following description taken in connection withthe drawings in which the single figure is a schematic diagram andelevational view partly in section of a picture pickup arrangementembodying my invention.

Referring in detm to the drawings, the picture pickup tube, which ishere shown as a modified image orthicon, comprises an evacuatedcontainer 1 having a photoelectric screen 2 on its inside surface at oneend on which the image of the view 3 to be transmitted is focused by asuitable optical system symbolized at 4. The electron image thusgenerated is accelerated by a grid electrode 5 into incidence with athin screen 6 of glass or other suitable insulating material. A focusingcoil symbolized by '77 may be provided to cause the electrons of theelectron image to move in parallel lines parallel to the axis of thecontainer 1, so that they strike screen 6 with the same distributionover the cross section of the image as they had in leaving thephotoelectric surface 2 at which they originated. The potential ofelectrode 5 is so adice justed that each electron striking screen 6causes the expulsion of one or more secondary electrons, and thus leavesa positive charge on the point where it struck the latter. Thecollective effect of all electrons striking screen 6 is therefore toimpart to the various points on the latter positive charge distributionwhich is a replica of the electron distribution in the electron image,which in turn is, of course, a replica of the light field distributionon input screen 2. In short, screen 6 quickly acquires anelectric-charge image which is a replica of the picture to betransmitted.

On the reverse side of screen 6 is incident a beam of electronsemanating from an electron gun 8 of a type too well known in the art torequire detailed description here. This electron beam is caused to scanthe glass screen 6 by some such means as deflecting coils 9. Itselectron content is made great enough so that it is able, while movingover any point on screen 6, to neutralize the entire positive chargewhich has accumulated thereon, in the manner described above, during thetime of one scanning cycle. Thus, when the spot on which the electronbeam is incident at any instant is one with a high positive charge, mostof the beam electrons will be absorbed by screen 6; but at anotherinstant of the scanning when the beam is incident on a spot of little orno positive charge, few or no electrons will be abstracted from thebeam.

In either event the beam electrons which are not absorbed by screen 6will find their way to an annular collector electrode 11 from which theyexpel secondary electrons, and these are attracted by a suitable voltageimpressed by a source 11A to a fluorescent screen 12 which they exciteto luminescence which is proportional at any instant to the number ofsuch non-abstracted beam electrons. The light flux from fluorescentscreen 12 thus varies in time in the same way that the electric chargeimage on screen 6 varies in space; that is to say, light fromfluorescent screen 12 varies in time in the same way as the light imageon input screen 2 varies in space, point by point. The number ofsecondary electrons expelled from collector electrode 11 exceeds thenumber of incident electrons; hence, an amplifying action is produced.

A photomultiplier tube 13 is positioned with its photoelectric inputscreen closely adjacent the fluorescent screen 12. Such tubes arestandard articles of commerce and need no description other than thatelectrons generated from their photoelectric input screens aremultiplied by secondary emission from cascaded electrodes to produce anoutput current or" substantial volume proportional from instant toinstant to the radiation flux striking their input screens. The RCA type5819 sold by Radio Corporation of America, Rockefeller Center, New York,is one such tube. The fluorescent material on screen 12 may for examplebe zinc oxide and if the 5819 tube is used it may be desirable to inserta filter 14 to screen out the long persistence rays from screen 12,since the persistence of the fluorescent light after excitation shouldbe no greater than the time taken by the electron beam to pass over asingle point on screen 6. A type of photomultiplier tube which could beused without filter 14 would be one sensitive to ultra-violet butotherwise like the RCA type 5819.

While I have described my invention in connection with a modified formof 'unage orthicon, it may also be applied as a modified structure ofany tube such as the image isocon and iconoscope which embodies anelectron scanning beam from which electrons are abstracted in proportionto the brightness or" the picture element on which the beam is incidentat any instant as it scans the picture point by point.

I claim as my invention:

1. A single vacuum-tight container enclosing a screen to generate andform an electron-image corresponding to a space-distributed radiationfield, a continuous thin sheet of insulating material, means forprojecting said electron image generated on said screen by saidradiation field into, incidence with one side of said sheet, means toscan said sheet with an electron beam of cross section small compared toits area, a fluorescent screen in said container and means to bombardsaid fluorescent screen with electrons proportional to the remnantelectrons of said beam not abstracted from said beam by the charge onsaid sheet at the point thereof which the scanning beam strikes at anyinstant.

2. A single vacuum-tight container enclosing; a photoelectric screenwhich emits electrons when irradiated; with a space-distributedradiation field, means for storing electric charges with a, spacedistribution corresponding' to. they electron image generated on saidscreen by said radiation field, means for projecting said electronimage. onto one side ofsaid storing means, means to scan'the oppositeside of said storing means with an electron beam of cross section smallcompared to the area of said storing means, means within said containerto, produce radiation in response to electron bombardmerit, means forprojecting electrons onto said radiation means. proportional at anyinstant to the remnant electrons not required to neutralize the chargeon said storing, means at the point thereof on which said scanning beamisthen incident and means for projecting saidradia'tion through a wallof; said: container.

' 3. A picture-reproducing tube enclosing a photoelectric screen whichemits electrons in response to radiations and. on which; a picture is tobe focused, a continuous thin sheet of glass, means for accelerating anelectron image generated on said screen by and corresponding tosaidpicture into incidence upon said. sheet, toscan saidsheet with anelectron beam of cross section small compared to the area of saidsheet,a fluorescent screen in said container and means to bombard.

said fluorescent screen with electrons proportional to thercmnantelectronsof said, beam. not abstracted from said-, b eam by thecharge on said, sheet at the point thereof which the scanning beam,strikes at any instant 4. A picture-reproducing tube enclosing aphotoelecscreen which emits electrons in response to radiations andi onwhich a picture is to be focused, means for storing electric charges,means for projecting an electronimage generated by said screen onto oneside of saidstoring means for forming a charge distribution thereoncorresponding to said electron image generated on said screen by saidpicture, means to scan saidstor-.

ing means with an electron beam of cross section small compared to thearea, of said charge-storing means, means. within said container, toproduce. radiation in response to. electron bombardment, means forprojecting electrons ontosaid radiation means to produce radiatiorrproportional atany instant. to the. remnant electrons not required; toneutralize the charge onsaid storing means at the. point'thereof onwhich said scanning beam isthenincident andmeans for projecting saidradiation through a wall of said container.

5; A single vacuum-tight. container containing means for producing anelectron image. with a space distributior1 v corresponding to that of aradiation field to be graphicallyportrayed, a thin glass. sheet,means-to project said imageinto incidence. upon one side of said sheet,means tofscanthe other side of said sheet with an electron bearn ofcross. section small compared to the area of saidsheet, a fluorescentscreen in said container and meansto bombardtsaid fluorescent. screenwith electrons propoitional-to the remnant electrons. of saidbeamnotabstracted from said beam by the charge on said sheet atthepointthereof which the scanning-.beam.strikes at any instant.

6. In combination with a single.vacuum-tightcontainer enclosinga.photoelectric screen which emits electrons in response to radiation andwhich is irradiated with a spacedistributed radiation field, means forstoring electric charges, means for projecting an electron image with aspace distribution corresponding to the radiation field generated insaid screen onto said storing means, means to scan said storing meanswith an electron beam of cross section small compared to the area ofsaid storing means, means for generating radiations in response toelectron bombardment, means for bombarding said radiation means withelectrons proportional to the remnant electrons from said beam, means toproject said radiation from said container which is proportional at anyinstant to said remnant electrons not required to neutralize the chargeon said storing means at the point thereof on which said scanning beamis then incident and a photoelectric amplifier system positioned so thatits photoelectric input screen is irradiated by said radiation from saidcontainer.

7. In combination with a picture-reproducing tube enclosing aphotoelectric screen which emits electrons on which a picture is to befocused, means for storing electric charges, means for projecting anelectron image corresponding to said picture onto one side of; saidstoring means with a space distribution corresponding to said.

electron image generated on said screen by said picture, means to scanthe other side of said storing means with an electron beam of crosssection small compared to. the area of said charge-storing means, meansgenerating.- radiation from said container in response to electronbombardment, means for bombarding said radiation means with electronsproportional at any instant to the remnant electrons not required toneutralize the chargev on said storing means at the point thereof onwhichsaid scanning beam is then incident and a photoelectric. amplifiersystem positioned so. that its photoelectric input screen is irradiatedby said radiation from said container.

8, Incombination with a single vacuum-tight container enclosing aphotoelectric screen which emits. electrons and which is irradiated;with a space-distributed radiationf eld, means for storing electriccharges, means for projecting. the electron image generated by saidscreen.

into incidence with one side of said storing. means to obtain a chargepattern on said storing means with a space distribution correspondingvto the electron image generated on said screen by said radiation field,means to, scan said storing means with, an. electron beam ofcrosssection small; compared to the area, of said storing Ineans, means,to produce radiation in: response to.electron bombardment, means tobombard said. radiation producing means with the remnant electron fromsaidv beam, means to project radiation. from said container which isproportional atany instant tothe remnant electrons not required toneutralizethe charge on said storing means at the point thereof onwhich. said scanning beam is then incident; and;. a; photomultipliertubepositioned to have its; input. screen irradiated bysaid radiationfrom said nta ner- 9, In; combination with a. picture-reproducingtubeenclosinga photoelectric screen which emits electrons and on which apicture is to be focused, means for storing electric charges, means forprojecting. an electron image generated by said, screen, into incidencewith one side of said; storing, means, the impingement of said electronimagesetting, upacharge image having a spacedistribution, correspondingto the electron image generated on said screen by said picture, means toscan the other side of said storing; means with an electron beamof crosssection small; compared to the area of saidcharge-storingmeans,afiuorescent-screem means for projecting theremnantelectrons on said. fluorescent screen, means to Project radiationfrom said: fluorescent screen which is proportional atany instantv tothe remnant electrons not required: to neutralize the charge on saidstoring means incident and aphotomultiplier tube positioned to have itsinput screen irradiated by light from said fluorescent screen.

10. A single vacuum-tight container enclosing an electron emissivephotoelectric screen to be irradiated with a space-distributed radiationfield, means for storing electric charges, means for projecting anelectron image generated by said screen into incidence with one side ofsaid storing means to form a space distribution charge pattern thereoncorresponding to the electron image generated on said screen by saidradiation field, means to scan the other side of said storing means withan electron beam of cross section small compared to the area of saidstoring means, a fluorescent screen in said container, means to bombardsaid fluorescent screen with electrons proportional to the remnantelectrons of said beam not abstracted from said beam by the charge onsaid storing means at the point thereof which the scanning beam strikesat any instant, and means to make the number of said electronsbombarding said fluorescent screen greater than the number of saidremnant electrons.

11. A picture-reproducing tube enclosing an electron emissivephotoelectric screen on which a picture is to be focused, means forstoring electric charges, means for projecting an electron imagegenerated by said screen into incidence with one side of said storingmeans to form a space distribution charge pattern thereon correspondingto the electron image generated on said screen by said picture, means toscan said storing means with an electron beam of cross section smallcompared to the area of said charge-storing means, a fluorescent screenin said container and means to bombard said fluorescent screen withelectrons proportional to the remnant electrons of said beam notabstracted from said beam by the charge on said storing means at thepoint thereof which the scanning beam strikes at any instant, and meansto make the number of said electrons bombarding said fluorescent screengreater than the number of said remnant electrons.

References Cited in the file of this patent UNITED STATES PATENTS2,149,487 Zilberman et a1. Mar. 7, 1939 2,248,977 Flory et al. July 15,1941 2,277,246 McGee et al Mar. 24, 1942 2,288,766 Wolfi July 7, 19422,402,058 Loughren June 11, 1946 2,460,471 Schade Feb. 1, 1949 2,582,831Hester Jan. 15, 1952 2,618,758 Cage Nov. 18, 1952

